implemented escapeString

src/Network/GemServ.hs

@@ -25,9 +25,11 @@ License along with this program.  If not, see
 -}
 
 module Network.GemServ (
-  encodeRequest
+  encodeRequest,
+  escapeString
 ) where
 
+import Data.Char (ord)
 import Data.List (intercalate)
 
 import Network.GemServ.Types
@@ -45,4 +47,21 @@ encodeRequest req =
       "" -> ""
       q  -> '?' : q
 
+-- | add required escape sequences to a string
+escapeString :: String -> String
+escapeString = concatMap $ \ch ->
+  if ch `elem` unescaped
+  then [ch]
+  else '%' : toHex ch
+  where
+    unescaped = ['0'..'9'] ++ ['A'..'Z'] ++ ['a'..'z'] ++ "~-_."
+    toHex ch  = let
+      n    = ord ch
+      high = n `div` 16
+      low  = n `mod` 16
+      in [hexDigits !! high, hexDigits !! low]
+
+hexDigits :: String
+hexDigits = ['0'..'9'] ++ ['a'..'f']
+
 --jl